Photosynthesis

Question 1

Chlorophyll a:-

Answer 1

Main pigment, contains magnesium ions. Is sometimes replaced by bacteriochlorophyll which contains manganese instead.

Question 2

Acessory pigments:-

Answer 2

All other than chlorophyll a, e.g xanthophyll, carotene, chrophyll b.

Question 3

Chlorosis:-

Answer 3

When Mg^2+ deficient plants show yellow leaves.

Question 4

Absorption spectrum:-

Answer 4

The quantity of light energy a particular pigment absorbs of each wavelength.

Question 5

Action spectrum:-

Answer 5

Rate of of photosynthesis of different wavelengths of light.

Question 6

Why do plants have different pigments and not just chlorophyll a?

Answer 6

Increases the range of wavelengths that can be absorbed, increasing photosynthesis efficiency.

Question 7

Wavelengths absorbed:-

Answer 7

Mainly red and blue, but overall, all except green.

Question 8

Engelmann’s experiment:-

Answer 8

Used spirogyra cell w/ spiral chloroplast.
When light split by prism, bacteria congregated where red or blue parts hit, indicating greater O2 release via photosynth at these sites.

Question 9

Antenna complex structure:-

Answer 9

Cone shape, in thylakoid membrane. Primary pigment reaction centre at bottom, acessory pigments layered arround outside, arrows to each one. Converge at PPRC. Overall = photosystem.

Question 10

Rf equation:-

Answer 10

Distance travelled by pigment/ distance travelled by solvent front.

Question 11

Photolysis:-

Answer 11

Splitting of water molecules into O2 and H2 by light. Relies on chlorophyll a photoactivation- the light absorption causes electron loss and thus a positive charge. Electrons to replace these are extracted from water, causing splitting and production of protons and oxygen.

Question 12

Photolysis equation:-

Answer 12

2H2O -> 4H+ + 4e- + O2

Question 13

H+ from photolysis:-

Answer 13

Used to reduce NADP^+ to NADPH

Question 14

O2 from photolysis:-

Answer 14

Given off as a waste gas or used in respiration.

Question 15

Light dependent stage location:-

Answer 15

Thylakoid membrane.

Question 16

Photophosphorylation:-

Answer 16

Light absorbed by chlorophyll a provides energy to convert ADP and Pi to ATP.

Question 17

Non-cyclic photophosphorylation:-

Answer 17

Photophosphorylation using the 2 photosystems.

Question 18

Cyclic photophosphorylation:-

Answer 18

Occurs in green plants when there is enough ADP and Pi available, only uses photosystem 1. Energy from excited electrons used to make ATP, not reduce NADP to NADPH2

Question 19

Calvin Cycle top:-

Answer 19

Enzyme rubisco catalyses the fixation of CO2.

Question 20

Calvin Cycle 1/2 o clock:-

Answer 20

6 carbon intermediate attached to enzyme formed.

Question 21

Calvin Cycle 3-5 o clock:-

Answer 21

Intermediate released and breaks down into GP (3 carbons, 1 phosphate group).
Also, curvy arrows w/ NADPH2-> NADP and ATP -> ADP + Pi.

Question 22

Calvin Cycle 6 o clock:-

Answer 22

GP reduced to GALP (a triose phosphate).

Question 23

Calvin Cycle 7-9 o clock:-

Answer 23

5C RuBP regen, ATP-> ADP + Pi happens.

GALP branches off.

Question 24

Calvin Cycle 10-11 o clock:-

Answer 24

CO2 molecules enter.

Question 25

GALP from Calvin Cycle:-

Answer 25

GALP-> glucose-> carbohydrates(inc sucrose), lipids and amino acids (combo w/ nitrates))

Question 26

Light independent stage summary:-

Answer 26

CO2 is fixed (converted into biochemical products in the plant). CO2 converted by enzymes into glucose. Reactions use ATP and NADPH2 produced by LDS.

Question 27

LIS in the dark:-

Answer 27

Calvin Cycle can take place in dark if sufficient ATP and NADPH2 are available. Most of the time, however, these are only sufficiently available in light as it is produced by light dep stage.

Question 28

Law of liniting factors:-

Answer 28

When a physiological process depends on more than 1 essential factor being favourable, its rate at any given moment is limited by the factor in shortest supply and that factor alone.